Gasoline reforming catalysts preparation



United States Patent REFORMING CATALYSTS PREPARATION GASOLINE NoDrawing. Application June 8, 1955 Serial No. 514,129

Claims. (Cl. 252--442) This invention relates to gasoline reformingcatalysts. In a specific aspect it relates to a method of preparing asupported platinum reforming catalyst. In another aspect it relates to amethod of preparing a platinum reforming catalyst on a particularalumina base.

This application is a continuation-in-part of my U. S. patentapplication Serial No. 434,680, filed June 4, 1954, which is directed toamethod of preparing a platinum on alumina reforming catalyst byimpregnating an alumina base with fluosilicic acid and chloroplatinicacid. It has since been found that asuperior platinum reforming catalystcan be prepared on a particular alumina by a novel method which is in'certain limited respects similar to the method disclosed in myco-pending application. I have discovered that a superior catalystresults when I employ my novel impregnating method anda particularalumina base, namely, an alumina which is prepared by the action of adilute solution of hydrogen peroxide upon amalgamated aluminum. Themethod of preparing the novel alumina is described and claimed in U. S.

' patent application Serial No. 514,125, of Charles E.

Welling, filed June 8, 1955.

The catalyst of thepresent invention comprises an alumina base,preparedbythe action of the dilute hydrogen peroxide solution uponamalgamated aluminum, having incorporated therewith about 0.0ll'%fluorine and about 0.01-.1% silica and having the requisite amount,usually 0.1l% of platinum, uniformly distributed throughout the alumina.The platinum concentration will always be the minimum per cent by weight'which will produce the desired upgrading of the feedstock. The novelmethod of preparing the catalyst comprises incorporating small amountsof silica and fluorine with the alumina base simultaneously with theincorporation of a platinum compound, and uniform deposition'of theplatinum throughout the, base. The finished catalystis capable ofproducing higher. octane reformates than conventional alumina-platinum,alumina-halogen-platinum catalysts, or catalysts prepared by the methodof my copending application upon other alumina bases.

A s hereinabove set forth, the-catalyst of the present inventioncomprises the particular alumina, fluorine, platinum and up to about 1%by weight silica. The base, or that part. of the present catalystexclusive of metallic platinum, is not to be confused with conventionalsilica-alumina cracking components which are often employed as reformingcatalyst bases, as disclosed in Patents No. 2,550,531, No. 2,651,598,and in PatentNo.

. 2 is not clearly understood. However, the small amount of silicaindicated has a definitely beneficial effect upon the performance andstability of the catalyst.

The particular alumina base employed in the present invention is a hard,porous, high surface area alumina. It is prepared by contactingamalgamated aluminum with a dilute aqueous solution of hydrogenperoxide. The reaction between aluminum and hydrogen peroxide "isallowed to continue, while agitating the mixture until the metal isconsumed or until no more aluminum reacts. Agitation is then suspendedand the mixture is allowed to stand for a period of time during whichthe newly formed alumina settles. A major portion of the supernatantliquid may then be decanted and the remaining liquid removed byfiltration. Alternatively, upon completion of the reaction, the mixturemay be charged to a filter without settling and decantation and thealumina recovered as a wet filter cake. In either case the filter cakeis then dried to form a very hard, porcelain-like,

yet porous alumina which is easily broken and sized and which may thenbe impregnated in accordance with'the method of the present invention.If desired, the filtered alumina may be mixed with a solution of theimpregnating compoundsto form a thick paste which may then be easilyextruded or shaped without a binder.

The degree of hardness of the alumina is a function of the concentrationof hydrogen peroxide in the treating solution. The most desirablealumina from the 'standpoint of hardness,'porosity and surface area isprepared with hydrogen peroxide. solutions containing 1-4% by Weight H 0As the hydrogen peroxide concentration in the solution is increasedabove 4%, the hardness of the alumina decreases rather sharply, and theresulting alumina isnot a satisfactory catalyst base. In mostinstances,'the hydrogen peroxide solution concentration is desirablyabout 3% by weight of H 0 The hardness of the alumina is also related tothe weight ratio'of' amalgamated aluminum to hydrogen peroxide solutionof 'any given H 0 concentration. Within the above specified limits, thehard, porous, alumina particularly well suited as a platinum reformingcatalyst basecan be prepared when the initial weight ratio of-aluminumto hydrogen peroxide solution is between" about 12100 and 1:25.Employing a solution containing about 3% by weight H 0 the weight ratioof aluminum to hydrogen peroxide solution isdesirably between about 1:60and 1:80.

' In accordance with the present invention, the alumina thuspre'pa' re'dis impregnated simultaneously with platinum, fluorine and silica from amixed aqueous solution of a readily soluble platinum compound, such aschloroplatinic acid, and a soluble silicon and fluorine-contain-2,478,916. .In these patents the silica content of the base is of theorder of at least 80% by weight, and alumina is present in amounts .upto about20%. Thesilica-alumina cracking component bases of the prior artcontain a major portion of silica. The present invention contemplates acatalyst base containing a major proportion of theparticular-alu'mina,up to 1% fluorine, and. not more than 1% by weight silica. The exactfunction'of the small amount of silica'and the manner in which itcontributes to the'elfectiveness of this superior catalyst ing compound,namely fluosilicic acid. Each of the com ponentsof the mixed solution,e. g. chloroplatinic acid and fluos ilicic acid, are present in amountsufiicient to incorporate the above-specified quantities of platinum,fluorine, and silica. mina is dried and then the adsorbed platinumcompound is converted to metallic platinum by reduction in a stream ofhydrogen at about 300-600 F., or by calcination in air at about 800-1200F. H

While platinum, fluorine and silica are alwayssimultaneously,incorporated with the alumina, the present in ventionis-,not limited to anyparticular physical'configuration or size of thealuminatreated. For example, .thenewly formed alumina may be impregnatedwith the mixed solution prior to initial drying, as by forming a paste.with'a small/volume of impregnating solution and extruding to formstrandswhich maybe dried and cut'to' uniform size. Alternatively, theparticularaluminalmay bedried and groundtoa veryfine powder, which isthentreated with azsolution of chloroplatinic acid and Followingimpregnation, the alufluosilicic acid. The impregnated powder may thenbe fed to a pilling machine and the resulting pellets calcined orreduced in hydrogen to form the final catalyst. On the other hand, theparticular alumina may be shaped or pilled (%a" x /8" to A" x /z") orcoarsely ground (6-12 mesh) prior to impregnation. In many instancesthis latter procedure is preferred because platinum losses are at'aminimum. When alumina is impregnated prior to shaping, there isconsiderable dusting and breakage during subsequent pilling or cuttingof the extrusions, and the losses of platinum are significant.

In order to uniformly impregnate the individual pills or similar shapesor coarsely ground alumina granules throughout with platinum either byspraying or immersion techniques, it is necessary that the mixedimpregnating solution be acidified with hydrochloric acid. If this stepis not taken, virtually the entire platinum content of the individualalumina pills or granules is concentrated in a thin layer on thesurface, and the catalysts so formed are not considered satisfactoryfrom the standpoint of activity or catalyst life. An impregnatingsolution containing in addition to chloroplatinic acid and fluosilicicacid sufiicient hydrochloric acid' to form a solution between 0.1 and1.0 Normal with respect to HCl will effect uniform platinum distributionwithin the alumina pills or granules. The impregnating solution isdesirably between about 0.4 and 0.6 Normal with respect to I-ICl. Theaddition of HCl is unnecessary when very finely ground or undriedalumina is impregnated with the mixed solution.

The present invention will be more fully understood from the followingnon-limiting examples.

Example I A quantity of the particular alumina employed as the catalystbase in the present invention was prepared as follows:

Granulated aluminum in the amount of 270g. was amalgamated by immersionin 300 ml. of a 0.4% solution of mercuric chloride. Followingamalgamation, the aluminum was repeatedly washed with water and thenadded to a 16 liter battery jar equipped with a powerful stirrer andcontaining a mixture of 1.125 liters of 30% hydrogen peroxide solutionand 11.25 liters of water. The mixture was agitated for 24 hours, afterwhich a small amount of aluminum remaining unreacted was removed, andthe alumina was filtered from the reaction mixture. The filter cake wasdried for 48 hours at 230 F. to yield an extremely hard, compact, yetporous alumina product. The product was calcined for a period of fourhours at 800 F. X-ray diifraction analysis indicated that it consistedof a mixture of apha alumina monohydrate and a gamma-type alumina. Thecalcined alumina had the following properties:

Surface area M. /g 243 Pore volume cc./g 0.49

Pore diameter A 81 Particle density g./cc 1.08

Example II A catalyst, hereinafter referred to as catalyst 1, wasprepared as follows: A portion of the alumina of Example I was crushedand sized 8-12 mesh. An impregnating solution was prepared by adding 1 NHCl to 1.4 ml. of chloroplatinic acid (containing 0.311 g. Pt./ml.) to atotal volume of 75 ml. To this solution there was added 1.7 ml. of a 22%fluosilicic acidsolution. The

solution and dried for about 4 hours at about 230 F. Adsorbed platinumwas converted to the metallic state by reduction in a stream of hydrogenat about 450 F. to form the finished catalyst.

Examination of the cross sections of broken catalyst granules showedthem to be uniformly impregnated with platinum. Catalyst 1 contained0.374% FL, 0.15% F., about 0.1% SiO alumina and chlorine. The chlorinecontent was not determined by analysis.

Example III Another catalyst, hereinafter referred to as catalyst 2, wasprepared on the alumina of Example I in accordance with the method ofExample II, with the exception that the adsorbed platinum values wereconverted to metallic platinum by calcination in air instead of byhydrogen reduction. Following drying at about 230 F., the impregnatedalumina Was heated in a stream of air for a period of 1% hours duringwhich the temperature of the alumina was raised from 500 F. to 1100 F.The catalyst was then maintained in the air stream for 1 hour at 1100 F.

Catalyst 2 was found to be uniformly impregnated with metallic platinum,and analyzed 0.45% Pt., 0.15% F., and about 0.1% SiO Chlorine was notdetermined. Catalysts 1 and 2, both prepared in accordance with themethod of the present invention, contained essentially the same amountof platinum, but differed from each other in the method of conversion ofthe adsorbed platinum compound to metallic platinum.

In order to establish the superiority of catalysts prepared inaccordance with the present invention over catalysts prepared withoutsimultaneous impregnation with platinum, fluorine and silica, threecatalysts were prepared on the same superior alumina base forcomparison.

Example IV "A catalyst, hereinafter referred to as catalyst 3, wasprepared on alumina prepared as described in Example I in accordancewith'the method set forth in Example II, with the exception that theimpregnating solution did not contain any fluosilicic acid. It consistedonly of 1.4 ml. of chloroplatinic acid made up .to 75 ml. with 1 N HCl.The impregnated alumina was treated in a stream of hydrogen to effectreduction to metallic platinum. Catalyst 3 .contained 0.403% platinumuniformly distributed throughout. In this respect it was similar tocatalysts 1 and 2. However, catalyst 3 contained no fluorine nor silica.

j Example V 'T\vo additional comparative catalysts, hereinafter referredto as catalysts 4 and 5, were prepared on the'same superior alumina ascatalysts 1, 2 and 3. A

Catalyst4 was prepared by spraying 125 g. of alumina prepared asdescribed in Example I with 95 m1; of a solution of chloroplatinic acidmade by diluting with water 2.4 m1. of chloroplatinic acid containing0.311 g. Pt./m1. The impregnated alumina was dried for 16 hours at 230F. and reduced with hydrogen for 2 hours at 450 F. Examination of thefinished catalyst'showed that platinum was distributed only in a verythin skin on the surface of the granules. Catalyst 4 contained 0.664%platinum, considerably more than catalysts 1, 2 or 3.

Catalyst 5 was prepared by impregnating 84 g. of alumina, prepared bythe method of Example I, by immerimpregnating solution'was added to g.of the sized alumina contained in an evaporating dish, and approximately10-15 ml. of'excess impregnating solution remained after saturation ofthe base. The contents of the evaporating dish Were warmed almost to theboiling point and stirred for 20 minutes so that the impregnated aluminawas ,constantly -wetted by the excess solution. The impregnated aluminawas then'removed from the sion in ml. of chloroplatinic acidsolution,prepared by diluting 1.2 ml. of chloroplatinic acid containing0.311 g. Pt./ml. with water. Rapid selective adsorption occurred. Theimpregnated alumina was dried and reduced by the method described forcatalyst 4. The finished catalyst 5 contained 0.453% platinum which wasdeposited as a thin layer on the outer surface of the alumina granules.With respect to depth of platinum impregnation, catalyst 5 was similarto catalyst 4. The platinum concentration of catalyst 5 was of the orderof catalysts 1, 2 and 3.

Example VI Each of the catalysts 1 to 5 was tested for its ability toupgrade a low octane gasoline under actual reforming Each catalyst wastested in the same manner by passing a mixture of hydrogen and the abovenaphtha over a bed of 75 ml. of the catalyst in a tubular reactor. Theinlet temperature was 940 F. and the pressure 500 p. s. i. The hydrogento hydrocarbon ratio was :1, and the liquid hourly space velocity was3.0. Samples of the reformate were withdrawn after 72 and 200 hours onstream and the octane number determined. The following table presentsthe results of these tests.

6 fluosilicic acid in amount sutficient to form a final catalystcontaining 0.1-1.0% platinum, 0.01-1.0% fluorine and 0.01-1% silica,drying the thus impregnated alumina, and converting the adsorbedplatinum compound to metallic platinum.

3. A method of preparing a gasoline reforming catalyst comprising thesteps of contacting amalgamated aluminum with an aqueous hydrogenperoxide solution containing 1-4% by Weight H 0 in a Weight ratio ofaluminum to hydrogen peroxide solution between 1:25 and 1:100,separating the newly formed alumina from the supernatant liquid,contacting said alumina with an impregnating solution consistingessentially of chloroplatinic acid, fluosilicic acid and hydrochloricacid, said impregnating solution being 0.1-1.0 Normal with respect tohydrochloric acid, in amount suflicient to form a final catalystcontaining 0.1-1.0% platinum, 0.01-1.0% fluorine and 0.01-1% silica,drying the thus impregnated alumina, and converting the adsorbedplatinum compound to metallic platinum in a stream of air at about 800-1200 F.

4. A method of preparing a gasoline reforming catalyst which comprisescontacting alumina prepared by the action of dilute aqueous hydrogenperoxide upon amalgamated aluminum with a dilute impregnating solutioncomprising chloroplatinic acid and fluosilicic acid in Each of thecatalysts l, 2 and 3, having platinum uniformly distributed throughout,is superior to catalysts 4 and -5 which contain platinum only on thesurface. Catalyst 1 produced a reformate approximately 10 octane numbershigher than catalyst 4, which contained nearly twice as much platinum.Catalysts 1 and 2, prepared in accordance with the method of the presentinvention, are definitely superior to catalyst 3, which was preparedWithout fluosilicic acid in the impregnating solution.

I claim:

1. A method of preparing a gasoline reforming catalyst comprising thesteps of contacting amalgamated alumi* num with a dilute aqueoussolution of hydrogen peroxide, separating the newly formed alumina fromthe supernatant liquid, contacting said alumina with an impregnatingsolution comprising chloroplatinic acid and fluosilicic acid in amountsufficient to form a final catalyst containing 0.1-1.0% platinum,0.01-1.0% fluorine, and 0.01-1% silica, drying the thus impregnatedalumina, and converting the adsorbed platinum compound to metallicplatinum.

2. A method of preparing a gasoline reforming cataamount sufficient toform a final catalyst containing 0.1- 1.0% platinum, 0.01-1.0% fluorineand 0.01-1.0% silica, drying the thus impregnated alumina at 200-400 F.and

0 converting the adsorbed platinum compound to metallic lyst comprisingthe steps of contacting amalgamated aluminum with an aqueous hydrogenperoxide solution containing 1-4% by weight H 0 in a weight ratio ofaluminum to hydrogen peroxide solution between 1:25 and 1:100,separating the newly formed alumina from the supernatant liquid,contacting said alumina with an impregnating solution comprisingchloroplatinic acid and platinum.

5. A method of preparing a gasoline reforming catalyst which comprisescontacting alumina prepared by the action of dilute aqueous hydrogenperoxide upon amalgamated aluminum with an impregnating solutionconsisting essentially of a 0.1-1.0 Normal hydrochloric acid,chloroplatinic acid and flu-osilicic acid in amount sufficient to form afinal catalyst containing 0.1-1.0% platinum, 0.01-1.0% fluorine and0.01-1.0% silica, drying the thus impregnated alumina at 200-400 F. andconverting the adsorbed platinum compound to metallic platinum.

References Cited in the file of this patent UNITED STATES PATENTS2,449,847 Heard Sept. 21, 1948 2,475,155 Rosenblatt July 5, 1949 FOREIGNPATENTS 717,062 Great Britain Oct. 20, 1954 OTHER REFERENCES MellorsComprehensive Treatise on Inorganic Chemistry, vol. 5, New York (1924),pp. 204-206.

1. A METHOD OF PREPARING A GASOLINE REFORMING CATALYST COMPRISING THESTEPS OF CONTACTING AMALGAMATED ALUMINUM WITH A DILUTE AQUEOUS SOLUTIONOF HYDROGEN PEROXIDE, SEPARATING THE NEWLY FORMED ALUMINA FROM THESUPERNATANT LIQUID, CONTACTING SAID ALUMINA WITH AN IMPREGNATINGSOLUTION COMPRISING CHLOROPHATINIC ACID AND FLUOSILICIC ACID IN AMOUNTSUFFICIENT TO FORM A FINAL CATALYST CONTAINING 0.1-1.0% PLATINUM,0.01-1.0% FLUORINE, AND 0.01-1% SILICA, DRYING THE THUS IMPREGNATEDALUMINA, AND CONVERTING THE ADSORBED PLATINUM COMPOUND TO METALLICPLATINUM.